/Set-TimeZone: Sets the default time zone in a Windows image. Before setting the time zone, DISM verifies that the specified ...

/Set-TimeZone:
 
  Sets the default time zone in a Windows image. Before setting the time zone,
  DISM verifies that the specified time zone string is valid for the image.
  This command is not supported against an online image.

    Example:
      DISM.exe /Image:C:\test\offline /Set-TimeZone:"W. Europe Standard Time"